Nuisance Beaver

Techniques for Controlling Nuisance Beaver

The purpose of this manual is to provide information on the most effective techniques available for resolving beaver/human conflicts. It integrates a wide range of topics and issues pertinent to beaver damage control and serves as a valuable reference tool for members of the public who have beaver damage. Information on the history of beaver management in New York State, the natural history and habits of beavers, definition of beaver damage, liability concerns, permit requirements, importance of good landowner/DEC relations, standard procedures for handling beaver nuisance complaints, and the methods/options presently available to resolve beaver damage concerns will be addressed.

The North American beaver (Castor canadensis) has a long and interesting history of management in New York. Nearly extirpated in the early 1800s, beaver populations made a spectacular recovery during the 1900s. This was made possible through trap and transfer, harvest restrictions and habitat recovery. By the early 1940s beaver had reoccupied New York. Beaver/human conflicts increased as a result. In response, New York established a nuisance focused beaver management policy in 1944. Beaver populations were purposely held at low levels by long fur-trapping seasons. This approach, which lasted through the 1970s, minimized the benefits as well as the costs of beavers.

During the 1960s and 1970s, New York's wildlife biologists examined the wetland-wildlife benefits provided by beaver impoundments. Study findings led to major changes in beaver management. It was determined that the habitat and other benefits of beaver balanced many of the costs. Beaver population objectives for ecologically based management units were established with measures of human tolerance and habitat potential being the key factor in objective setting. The result was higher beaver population objectives. During the 1980s, beaver populations increased throughout much of New York State. Beaver populations were maintained at desirable levels by regulating the trapping seasons. The goal was to provide more wetland-wildlife benefits to New Yorkers.

Presently many of New York's wildlife management units are at or above the management objectives set for beavers. In 1993, it was estimated that there were about 17,500 active beaver colonies in New York. This was about 3,500 more than the statewide goal of 14,000 and an increase of 19% since 1990. Beaver damage was reported at about 2,000 sites, resulting in 5.5 million dollars worth of property damage. An additional $330,000 was spent by the State to handle these complaints.It is therefore important to take a more comprehensive approach to resolving beaver damage complaints by integrating current beaver damage control technology with in season trapping, permit issuance, standardized operation procedures and sound technical advice.

The beaver is the largest rodent in North America with adults ranging from 35 to 46 inches long (including a flattened 12-18 inch tail) and weighing from 45 to 60 pounds. Beaver weighing over 100 pounds have been recorded. The hind feet are very large with 5 long webbed toes. Front feet are small and dexterous, which allows the beaver to carry dam construction material such as stones and sticks.

Both sexes of beavers breed at 21 months of age from December through February. Females ovulate 2 to 4 times at 7 to 15 day intervals during each mid-winter breeding season. There are no records of beavers breeding as first year kits. Development of the fetuses requires 120 days with the young being born between April and July. Litter sizes range from 1 to 9 with an average litter size of 4. The heavier the female, the larger her litter, also the number of young a female bears is inversely related to her family size at the time of breeding. Adult females will breed every year regardless of the habitat quality.

The occupants of a beaver pond or group of ponds is a family consisting of two adults and their offspring of two breeding seasons. Beavers mate for life; however, if one of the adult breeding pair is removed from the population, the remaining member will readily accept a new mate. The kits remain with the parents until they are two years old and then are driven off to find their own territories. This dispersal of juveniles can contribute greatly to the total number of property damage complaints.

As a food source, beavers prefer aspens and willows but will eat the leaves, twigs and bark of most species of woody plants found along the water's edge. During the growing season beavers will also consume large quantities of non-woody plants such as grasses and cattails. During the fall, they will stockpile their woody food supply in the water near their house for use during the winter months. The presence of these fresh cut feed piles is an important indicator of an active beaver lodge. During the ice covered winter months beavers are generally inactive with regard to tree cutting and dam building.

Beavers construct dams which result in the formation of ponds within which the lodge and winter food cache are located. It is believed to be a combination of water flow sensation and the sound associated with running water that stimulates this dam building activity. Within and around the pond the beavers construct canals for security and for the transport of food and building materials. Beavers are primarily active at night with regard to their dam building and tree cutting activity.

The beaver's dam and lodge are constructed of sticks and mud, with some beavers utilizing bank burrows along streams or ponds. Lodges consist of one or more compartments with each compartment having two underwater openings for exit or entry. These are also important for escape from potential predators. Their aquatic habitat and instinctive behavior minimizes the adult beaver's susceptibility to predators. Domestic dogs, coyotes, bears and bobcats are among the larger predators in New York State that prey on beavers if the opportunity arises. However, since beavers rarely travel far from water, they are relatively safe from most predators. Young beavers are more susceptible, with predatory mammals such as otter and mink occasionally preying on kits. Overall, natural predation probably has little effect on beaver populations in New York State.

The impoundments created by beavers provide valuable wildlife habitat for assorted furbearer and waterfowl species. In this way, the beaver provides valuable ecological benefits to the public at large. On the other hand, the beaver's dam building activity can result in widespread flooding of woodlands and agricultural land and cause numerous complaints by plugging road culverts, flooding roads, railroad tracks and causing general property damage concerns.

Article 11 of the New York State Environmental Conservation Law is commonly referred to as the "Fish and Wildlife Law." Sections 11-0505 and 11-0521 of Article 11 address legal issues pertaining to managing beaver-related damage.

Section 11-0505 states that no person is allowed at any time to disturb a beaver's dam, house or den without written permission from the DEC. This permit will be issued to the person or organization which is being damaged or affected or may potentially be affected. If the permittee (affected party) does not own or legally control the site where the beaver's dam is located, it is the permittee's responsibility to obtain permission to go on lands he/she does not own or legally control to carry out the permitted actions.

Section 11-0521 authorizes the DEC to issue permits for the removal of nuisance beavers. This permit will be issued to the landowner upon whose land the problem is occurring, an adjacent landowner upon whose land the beaver resides or either landowner's agent. The permittee may designate in writing an agent who will kill the beaver.

There is also interaction between the alteration of a beaver dam (Article 11) and freshwater wetland (Article 24) permits. Article 24 of the Environmental Conservation Law, known as the Freshwater Wetlands Act, deals with the preservation and protection of freshwater wetlands within New York State. Section 24-0701 of this Article outlines situations requiring permits for removal of beaver dams within the protected areas of freshwater wetlands. Regulations governing implementation of Article 24 (NYCRR Part 663) (link leaves DEC's website) list "removing or breaching beaver's dams" as an activity requiring a permit both within a regulated wetland and its adjacent area. Certain activities, however have been identified as being exempt from Article 24 permit issuance. These include removal or alteration of beaver's dams impacting on agricultural activity and removal of beaver's dams causing flooding of existing structures.

Article 15 of the Environmental Conservation Law pertains to the protection and conservation of the water resources of New York State. Section 15-0501(1) of this Article states that, with certain exceptions, no person or public corporation shall change, modify or disturb the course, channel or bed, or remove any sand, gravel or other material from the bed or bank of any stream which has been designated by DEC as being "Class C(T)" water or higher class without a permit. If removal of beaver's dams in these protected streams results in any of these disturbances, an Article 15 permit is required.

To accommodate this requirement for Article 15/24 permit issuance, a general Article 15/24 permit for beaver dam alteration has been developed. Where applicable this general Article 15/24 permit should be issued for beaver dam alteration in freshwater wetlands and protected streams.

Problem beaver situations may include an impoundment threatening downstream property, upstream flooding of land, trees or crops killed or damaged by flooding, flooding of homes, flooding of highways or railroads, contamination of water supplies, impairment of drainage systems, damage to wildlife habitat or landowner distress.

In Barret v. State of New York (1917), the State Court of Appeals found that the State was not liable for property damage caused by wildlife. This landmark decision reversed an earlier judgement in a lower court which had awarded Barret compensation for damage to his property caused by beaver. The State of New York is, therefore, not legally liable for wildlife damage.

While it is ultimately the responsibility of the landowner to resolve the problem, the DEC will assist the public in finding appropriate solutions to problems caused by beavers. This will be done within the limits of DEC's legal responsibility, fiscal capabilities and priorities. It is important for the DEC to provide this assistance to minimize costly damage and generate public acceptance for beaver populations at sufficient levels to provide desired amounts of wetland/wildlife habitat.

The initial breaching of a beaver's dam can create a hazardous situation. To avoid washouts, water levels above and below beaver's dams should be equalized by slow and partial breaching before the entire dam is removed. Road culverts immediately downstream of a beaver's dam should also be inspected for size and condition prior to dam removal. Furthermore, water level control devices or guards should not be installed that restrict the water flow from the original culvert design unless a safe overflow is provided. This overflow potential can be created by placing tubes through dams or deep water fencing located upstream from road culverts. In this way, excess flood water will flow over the dam or deep water fencing and through the original road culvert. When giving technical advice, property owners and road maintenance personnel should be advised of the consequences of restricting designed water flows.

It would also be advisable to refrain from physically altering the beaver's site location in any way that might produce a hazard or danger. For example, caution should be taken when excavating deep water trenches adjacent to public road right-of-ways for control installation unless suitable barriers or guard rails are installed for protection. This should be discussed and agreed upon with the governmental agency responsible for maintenance of the road right-of-way.

Beaver's activity in artificial impoundments and marshes also present a special area of concern. The dikes of many such impoundments are often constructed of topsoil through which a pipe or water control box regulates water levels. Some of these dikes are also built with emergency spillways cut below the rim of the dike. These are designed to prevent washouts in the event the control box should become plugged. When both the primary water control and emergency spillway become, plugged by beavers, water levels will rise possibly resulting in overtopping and washout of the dike. The degree of hazard resulting from such a situation is dependent upon the height and stability of the dike, the acreage and depth of the pond and the proximity of roads or property immediately downstream of the dam site. With this in mind, water levels should not be maintained above the designed height of the emergency spillway or the top of the water control box or pipe. It would be best to consult with an engineer when asked for advice or service in controlling the level of a beaver pond involving an artificial dike.

Protect Trees and Shrubs

(Note. No permit is required.) Individual shrubs and trees can be protected by loosely wrapping to a minimum height of 36 inches with welded wire fencing, zinc or plastic coated, or roofing felt held in place with string or wire.)

Groups of shrubs or trees can be protected with 36 inch high fences made of welded wire, woven wire or 12 inch high tensile electrified wire with a minimum of 3 strands of wire spaced at 4 inch intervals.

(Note: Fencing may not be effective in late spring where deep late snow persists.)

Protect Road Culverts Against Blocking

It is not safe to constrict the flow of water through a road culvert. Culvert guards must be as open as possible, regularly inspected and cleared of debris. It is also extremely hazardous to stand in the water in front of a culvert while unblocking it or to crawl into one to open it. More information can be found in the publication Managing Nuisance Beaver Along Roadsides (PDF) (250 kB).

Pitchfork-shaped Guard

(Handout #3). This is made of heavy steel rods, welded 6" apart to 2 horizontal braces or a piece of 3 to 4 inch channel iron. This device is pushed into the bottom to hold it in place in front of the culvert. It is a preventive measure to keep wandering beaver from getting inside a culvert and plugging it.

Deep Water Fence

(Handout #4). These D-shaped or square fences, 10' to 20' on each side, made of 6" by 6" reinforcing steel mesh held by 6' steel fence posts. These are placed above intakes to prevent floodwater debris or beavers from blocking a culvert. If beavers place material against the fence, the resulting dam becomes a temporary emergency spillway which must be removed or modified because road grades should not be used as dikes. If a Water Level Control Device (WLCD) is to be used in a culvert, it should be used in conjunction with a deep water fence.

It is important to carefully select a location for installation of a water level control device (WLCD). Even where one can be successful, a complainant must be committed to the installation of a WLCD and it is likely to fail if not regularly inspected and maintained. Therefore, consider the following before installing a WLCD:

How does a WLCD function?

a. By excluding and regulating. The best devices keep beavers away from their intakes and regulate the water level in the pond. Some devices only delay the beaver from getting to the intake of the device and merely delay their plugging it.

b. The best devices muffle the sound of escaping water and make the sensation of flow undetectable. An example would be the Clemson tube or combination deep water fence and tubing. If the pond is drawn too low and the beavers are unable to neutralize the device, the beaver must build another dam upstream or downstream or abandon the pond.

c. The level at which a beaver pond may be held and have the beaver remain varies. The depth of the lodge or burrow entrance may be used to gauge this level.

Why should a WLCD be installed?

a. To prolong the life of a desirable beaver wetland. However, few sites can support beavers for more than a few years if young beavers are not harvested each year.

b. To resolve a dispute between adjacent property owners affected by the same beaver family. But one or both owners must agree to purchase materials and to assemble, install, and maintain the device.

Where can a WLCD be used?

a. Only in a beaver's dam that does not directly involve a water control box, dike, culvert, or man-made structure. Structures for retaining or passing water must handle runoff of severe storms and partial obstruction of these can be disastrous. Never restrict flow capacity from the original design. (Note: See Handout #6.)

b. Only in beaver's dams where temporary flooding will do little harm. A WLCD should not be installed where flooding to the original level cannot be tolerated. It is important not to underestimate the flow rate when installing tube style WLCDs. Inadequate size tubing will result in persistent flooding problems.

c. In areas where there is minimal opportunity for beavers to neutralize their effectiveness. A drainage that provides countless dam sites should be avoided. A WLCD should not be installed in a dam if there is a constriction in the topography downstream of the site.

d. In beaver ponds with pool depth of 4 feet or more. A WLCD can be installed in less water than this if the device disguises the flow of water into the intake and/or the intake is protected by an exclosure.

e. In ponds with clay or gravel bottoms. Soft mucky or silty bottoms allow beaver material for blocking WLCD intakes. This is especially true for WLCDs that have intakes that are not protected by exclosures or do not disguise the flow of water.

f. If Only in accessible sites. People must get to the site easily for construction, inspection, and maintenance.

Polyvinylchloride (PVC) pipe is quieter than most other suitable materials but is limited to diameters of 10" or less because of weight. The Clemson tube, made with this material, is especially effective.

Corrugated Flexible polyethylene tubing must be protected from beavers chewing by wrapping with chicken or welded wire, and tends to float so it must be staked up every 5 to 10 feet. It is also limited to diameters 10" or less but is the cheapest material available.

Corrugated galvanized steel pipe is limited to small diameters (less than 8") because of weight and high cost. It's more likely to attract beavers plugging because water causes excessive noise when passing through it.

Welded wire cylinders must be reinforced to prevent crushing by beavers and are seriously weakened by corrosion. They often become non-degradable litter because they are very difficult to remove. However, they are cheap, easily carried to remote sites and can be used for quick relief until a more suitable device can be assembled.

(Note: Prior to installing a WLCD in a beaver's dam, the pond level should be lowered to the installation height. Large amounts of water flowing through a narrow opening in a dam not only make installation more difficult, but can be dangerous as well. Depending on the physical characteristics of the pond, the length of time needed for drawdown may vary from a few hours to overnight.)

Combination Deep Water Fence/Ribing (Handout #7). This is a 10 foot square or larger rectangle made of heavy reinforcing mesh or welded wire fencing placed out in the deepest water of a beaver pond. A length of solid tubing is extended from the fence through the dam at the desired water level. The fence prevents the beaver from plugging the intake of the pipe, but sometimes they build a dam around it if they hear or feel the flow of water.

Clemson Pond Leveler (Handout #8). This is a perforated PVC tube within a welded wire tube and is installed so that the inlet is always submerged. It is designed so that the beaver cannot feel or hear the flow of water into the WLCD and don't try to block the intake. This device is suitable only for small watersheds and intermittent streams.

Pond Drain Tubes (Handout #9 and Handout #10). These WLCDs do not disguise the flow of water. They are usually suspended on posts (Y to 4) above the bottom of the pond. This helps to delay the beaver from building a dam around the intake. The harder the bottom, the longer the delay These WLCDs are less expensive and lightweight, but require more maintenance than other WLCDs.

Electric breach guard (Handout #11). This is a charged smooth wire fence with dangling bobs built in front of a dam to keep beavers away from a breach or away from a previously blocked culvert. This device provides a wide range of water level control. An expensive energizer and battery is required. The battery can be completely drained by. prolonged contact between a water-soaked log and the fence. Both it and the energizer are often stolen. For these reasons, this device is often ineffective if not inspected and serviced once each week.

Plans for additional water level control devices, available from the Snohomish County, Washington, Department of Public Works, can be accessed here (Snohomish County Plans) or from the link in the links leaving DEC's website box on the right side of this page.

Open Season--The trapper/landowner partnership is undoubtedly the best long-term solution for minimizing beaver damage. A trapper can solve a landowner's problem by trapping beavers during the open season. Beaver pelts are at their prime during these winter seasons. The Bureau of Wildlife maintains a list of active beaver trappers in your region. Trapping methods include the use of foot-hold and body-gripping traps.

Closed Season--Complainants must obtain an Article 11 permit from the Bureau of Wildlife to destroy beavers and/or their structures. Fees may be incurred to have trappers remove beavers during the closed season. Pelts are of no value at this time of year.

Methods of Take During the Closed Season--(Note: Complainants or their agents land owned or leased by the complainant, do not require trapping or hunting licenses).

Body Gripping Traps--Strike and hold target animals on the neck or chest.

Cables--(Note: These methods are lawful ONLY under authority of an Article 11 permit.) Loops of light cable are suspended in channels or in front of burrows to catch beavers swimming through.

Cable clusters of four or more small loops of wire are extended from a pole which can serve as bait and anchor. Beavers attracted to a freshly cut aspen pole become entangled in the loops.

Shooting--Bullets or shot discharged over water are likely to ricochet beyond the target. Firearms may not be lawfully discharged within 500 feet of a farm, building, or dwelling, without the consent of the owner, or within 500 feet of any school or playground, over any public highway or in a municipality with a law forbidding it.

A nuisance beaver can usually be attracted to a breach in its dam, where shooting will be safe. A shotgun with number four buck is recommended. Beavers are more likely to inspect a breach early in the morning or late in the evening. If the shooter misses, the beaver seldom provides another chance.

Except under authority of an ECL Title II Permit, it is unlawful to disturb any structure made by a beaver. A complainant or agent who breaches a beaver's dam under such permit authority is personally liable for any flooding damage done to downstream property.

If the beaver is not killed, dam removal is a very short-term solution. Beavers usually rebuild dams quickly and sometimes in larger volume. Beavers are most active at night, therefore, dams should be breached in the morning to allow water to flow all day.

The draining of beaver ponds is more successful during the dry summer months when there is less available water to resupply ponds that are being drained. Ponds that are supplied by seasonal runoff can sometimes be drained during dry periods so as to discourage beavers and cause them to relocate.

After beavers are removed and the water has been drained from the pond, it is advantageous to remove as much of the dam as possible. A narrow notch in the dam of an abandoned pond is very easily plugged by wandering beavers.

Hoeing by hand--Potato hoes or stone hooks are the best tools. Shovels and spading forks are ineffective. Good water control is possible if the breach is kept shallow and broad so that the water level falls slowly. In the case of a large blocked culvert (2' diameter or greater) it is very unsafe to stand in the water in front of it or crawl into it from the other end.

Power Excavating--Tractor or truck mounted excavators are often used by town, county or state highway employees to remove large amounts of material from beavers' dams and can inadvertently cause down-stream flooding.

Blasting--like hand tools, explosives are easily carried to inaccessible sites (Caution: Users of explosives must be licensed). Using explosives to breach a beaver pond is, unfortunately, almost certain to cause down-stream flooding and excessive siltation and is seldom justified. Neighbors should be told where, when, and why this is going to be done. If this method must be used, it is best to do it in mid-summer when the water is low.

This is sometimes done in the hope of driving beavers out or to discourage other beavers from occupying the pond site in future years. (Note: It is unlawful to disturb a structure made by a beaver, EXCEPT under a permit which clearly gives authority for this action.) Destroying an occupied lodge seldom causes a beaver family to leave. However, after the beaver have been removed and the pond drained, it may be advantageous to destroy the lodge so that the site is less of an attractant.

(Note: Abandoned beaver lodges have some value as habitat for other wildlife.)

More about Nuisance Beaver:

Controlling Beaver Damage - Solving beaver problems, the biology and behavior of the North American beaver (Castor canadensis), and the pitchfork guard.

Deep Water Fence for Beaver - The purpose of the deep-water fence is to physically exclude beavers from plugging the intakes of road culverts